The present invention relates to a precision machining device suitable for use in a data recorder arrangement to achieve increased data recording density. More particularly, the invention relates to a machining device which uses a scanning probe microscope capable of observing substances ranging from conducting materials to insulating materials, as well as to a recording device for recording and reproducing large amounts of data at a recording density, for example, on the order of tera-bit per square inch.
The use of magnetic and optical disks to record data is well known. Due, however, to factors such as spacing required between the recording head and the recording medium, a practical limit on detected output, and a diffraction limit, it has been considered that about 100 Gb/in.sup.2 is a limit to a recording density. If recording density continues to grow at the present rate, it is expected that the limit of recording density will be reached early in the twenty-first century. Therefore, the development of a new data recording technology of the Tb/in.sup.2 order toward the twenty-first century has been urged.
Under such circumstances, precision machining technology using a scanning probe microscope (SPM) is drawing attention. One such machining arrangement uses a scanning tunneling microscope (STM), such as disclosed in U.S. Pat. No. 4,343,993.
A surface machining and recording device using the STM is disclosed in Japanese Patent Laid-Open No. 08536/1986. In that device, the recording method consists of adsorbing atoms on a crystal surface or desorbing atoms from the crystal surfaces by means of an electron beam generated by a conventional electro-optical device such as employed in an electron microscope, or by utilizing a tunnel current from the tip of the STM. The presence and absence of adsorbed atoms are allowed to correspond to "1" and "0" of recorded data. The reading method consists of reading the presence or absence of the adsorbed atoms by using the STM.
The above-mentioned prior art is characterized by a number of problems. First, the precise machining technology using the STM requires a clean sample surface at low temperatures, in a controlled environment which is free from external effects, such as a deep vacuum. Furthermore, prior art devices using STM require the use of a conductive material as a recording medium. That is, insulating materials cannot be utilized as a recording medium, which poses a significant limitation on the selection of a medium.
Another surface machining device using STM technology is described in "Physical review letters" Vol. 65, No. 19, pp. 2418-2412. In this prior art, the machining process is performed at standard atmospheric conditions, but the sample is expensive gold. Although the recording medium is generally handled in the ambient atmosphere, and many kinds of conductive material such as Al or Si can be used, such materials easily oxidize in the air, creating an insulating surface.
It is thus necessary to develop a method and apparatus that can write data by precision machining on a substrate having an electrically insulating surface, at recording densities on the order of Tb/in.sup.2. While such a high recording density requires a recording medium which has a large flat surface, the technology to provide a semiconductor substrate such as Si having a large flat face is established. And such substrate is suitable for use as a commercial recording medium, because it is relatively inexpensive.
One object of the present invention, therefore, is to provide a fine-machining technology capable of achieving a precision on the order of nanometers (an atomic level), and of machining an insulating material. In particular, it is an object of this invention to provide such a data recording technology which is capable of writing and reading on any substances ranging from electrically conducting materials to electrically insulating materials.
In the above-mentioned Japanese patent document, the recording tip must be brought closer to the surface of the recording medium during data recording than during the ordinary operation of such a device, thus increasing data recording time in applications where high-speed operation is required.
Another object of the present invention is to provide a data recording technology which is capable of stably operating at a standard atmospheric pressure and at a normal temperature, and which is capable of accomplishing high-density recording with a recording unit on the order of nm (atomic level), at high speed.